the tech flex loom that is on my car came from Ebay, you can get it in so many different sizes that it is just easier to buy the sizes you need. I have 5 different sizes in my car as well as some of the split stuff for things i did not want to undo. many of the Ohio guys as well as others have had great luck from this seller. 1/8" and 1/4" seemed to be the more popular sizes when i did my bay, but i bought 1/2" stuff to cover larger wires as well. I bought over 50ft of 1/4 but i did speaker wires and interior wires with it as well.
for redoing the engine bay you will have enough to cover all the wires properly, you should have enough to cover interior wires that you change also but its always nice IMO to have more than needed. Just make sure you get all the heatshrink to finish the wires properly as well.
